Unglazed terracotta cooling flagon (Gurusia) thermodynamics: evaporative water chill rates?

The cooling mechanics of the traditional Sri Lankan terracotta water carafe (Gurusia / Kulahediya) rely entirely on evaporative latent heat transfer. Potters formulate clay using alluvial river silt mixed with 15% fine quartz sand, firing pieces at low temperatures (750-800°C) to prevent complete vitrification. This preserves microscopic open capillary pores through the earthenware body. Water seeps slowly to the exterior vessel surface, where ambient dry-zone winds evaporate the thin water film. The phase change consumes heat energy from inside the carafe, dropping water temperature by 3°C to 5°C below ambient.